i965/blorp: Only do offset hacks for fake W-tiling and IMS

i965/blorp: Only do offset hacks for fake W-tiling and IMS

Since the dawn of time, blorp has used offsets directly to get at different
mip levels and array slices of surfaces.  This isn't really necessary since
we can just use the base level/layer provided in the surface state.  While
it may have simplified blorp's original design, we haven't been using the
blorp path for surface state on gen8 thanks to render compression and
there's really no good need for it most of the time.  This commit restricts
such surface munging to the cases of fake W-tiling and fake interleaved
multisampling.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>